Objective To observe the effects of electroacupuncture(EA)at "Zusanli" (ST36) on the ultrastructure and mitochondrial dynamics of skeletal muscle tissue in spleen qi deficiency rats

so as to explore the partial action mechanism of EA at ST36 for spleen deficiency syndrome.Methods Twenty-four male SD rats were randomly divided into 4 groups:normal group

model group

ST36 group and non-acupoint group(n=6 in each group).The model of spleen qi deficiency syndrome was established by improper diet and exhaustive swimming.EA(2 Hz/15 Hz

0.5 mA)was applied to bilateral ST36 in the ST36 group and non-acupoint in the non-acupoint group for 20 min

once daily for 7 days.The colorimetric method was used to detect the ATP content in skeletal muscle tissue.The ultrastructure changes of skeletal muscle tissue were observed by transmission electron microscopy.The expression levels of optic atrophy 1(Opa1)and dynamin-related protein 1(Drp1)mRNA and proteins in the skeletal muscle tissue were determined by fluorescence quantitative real-time PCR and Western blot

respectively.Results The ATP content in skeletal muscle tissue of model group was significantly lower than that in the normal group(P<0.05)

while significantly higher in the ST36 group than that in the model group and non-acupoint group(P<0.05).Transmission electron microscopy showed that a large number of muscle fibers that were ruptured

damaged

and disorganized;moreover

many vacuoles with different sizes

and abnormally shaped or swollen mitochondria were observed in the model group.ST36 treatment improved the disordered fiber arrangement

and reduced the population of damaged mitochondria;thus

fused and elongated mitochondria were readily observed.Compared with the model group

there were no obvious improvements in the non-acupoint group.Compared with the normal group

the expression levels of Opa1 and Drp1 mRNAs and proteins in the skeletal muscle tissue were significantly lower in the model group(P<0.05).After the treatment

the expression levels of Opa1 and Drp1 mRNAs and proteins were up-regulated in the ST36 group(P<0.05)

and the expression of Drp1 protein was up-regulated in the non-acupoint group(P<0.05).Conclusion EA at ST36 can correct the imbalance of mitochondrial fission and fusion in skeletal muscle of rats with spleen qi deficiency

thereby improving the damage of mitochondrial structure and function

and leading to an increase of energy metabolism.